1. Technical Field
The present invention relates to a carrier-separating and liquid-collecting mechanism for use in a liquid-waste treatment apparatus for biologically treating organic liquid-waste, such as sewage, human excrement and industrial liquid-waste, utilizing carriers having microorganisms immobilized thereon.
2. Description of Related Art
In recent years, as liquid-waste treatment techniques, an activated sludge method, a biomembrane method and an immobilized microorganism method have been known. From the viewpoint of efficient utilization of land, it has been desired to develop a liquid-waste treatment method which is space-saving, and a method for an aerobic treatment of liquid-waste utilizing carriers having microorganisms immobilized thereon and an improvement of performance of those carriers have attracted attention. The present inventors have been working on the development of an apparatus for biologically treating liquid-waste utilizing microorganism-immobilized carriers, and have encountered the below-mentioned technical problems during a process of the development.
That is, when microorganism-immobilized carriers flow through a treatment tank, together with a liquid to be treated, the concentration of carriers near an outflow end of the treatment tank becomes high, so that scum and contaminants (impurities) adhere to a carrier-separating and liquid-collecting mechanism in the form of a screen disposed at the outflow end of the treatment tank, thereby increasing the liquid level in the treatment tank. Consequently, the treatment tank must be cleaned intermittently, by using industrial water and the like. Thus, in the above-mentioned treatment tank, the treatment performance is lowered because a uniform distribution of the carriers cannot be maintained, and a blockage of the outflow end of the treatment tank occurs.